This application is a revised version (A1) of a competing renewal for years 06 through 10 of program project grant POI AG020677 (Aging Well, Sleeping Efficiently). Insomnia in older adults is a widely prevalent health condition that is associated with significant distress, functional impairment, increased utilization of healthcare, and high financial costs. The aim of the program is to identify novel physiological, electrophysiological, genetic and functional neuroanatomical correlates of insomnia in older adults. All projects will use treatment with Cognitive Behavioral Treatment of Insomnia (CBTI), as an intervention challenge to determine how changes in insomnia symptoms affect these correlates of insomnia. The program has four inter-related projects and three cores examining a group of 120 Older Adults with Insomnia (OAI) all receiving CBTI, as well as a demographically balanced group of 100 good sleepers (GS). All participants will be 60y+; both genders will be studied. Projects 1-3 will each examine a subset of the participants. Advertising for participant recruitment will be provided by Core A {Administration - Monk). All participants will be recruited, telephone pre-screened, consented for screening and screened using Core B (Clinical core - Buysse/Germain) resources, and then assigned to one of three different projects using procedures provided by Core C {Data Management and Statistics - Mazumdar/Hall). All participants will contribute to Project 4 {Genetics - Nimgaonl<at). Core B will also be responsible for delivering the CBTI and collecting clinical variables. Core A will provide general administration; Core C will handle data analysis and statistics. Project 1 {Circadian/homeostatic - Monk/Buysse) will involve a laboratory evaluation of circadian rhythms and sleep homeostasis using a sleep deprivation challenge; Project 2 {Hyperarousal - Hall) will use a series of laboratory challenges to evaluate the dynamic properties of psycho-physiological arousal; Project 3 {PET imaging - Nofzinger) will involve PET imaging during NREM sleep and wakefulness. Project 4 {Genetics-Nimgaonkar) will examine polymorphisms and functional properties of the Per3 gene, examining correlations between these polymorphisms and behavioral and physiologic variables. All four of the component projects essentially have two major aims: 1) to investigate baseline correlates of insomnia in older adults within their particular domain of interest; and 2) to determine whether these correlates also relate to the level of success of a non-pharmacological treatment for insomnia (CBTI). This Program Project will significantly advance our understanding of insomnia and its treatment in older adults.